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Chronic Hypertension with Pregnancy
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Chronic Hypertension with Pregnancy
Hypertension is the most common medical problem in pregnancy, complicating 3 to 15% of pregnancies and accounting for about 18-30% of all antenatal admissions. Hypertensive disorders in pregnancy are still one of a major cause of maternal, fetal, and neonatal morbidity and mortality in both developing and developed countries.
Chronic hypertension in pregnancy (CHP) is hypertension that is present at the booking visit or before 20 weeks or if the woman is already taking antihypertensive medication when referred to maternity services. It also includes high blood pressure, which lasts for longer than 12 weeks after giving birth. Chronic hypertension is also called pre existing hypertension in pregnancy. In contrast, new onset of elevated blood pressure readings after 20 weeks' gestation mandates the consideration and exclusion of preeclampsia. The prevalence rates of pre existing hypertension are increasing due to delayed childbearing.
Chronic hypertension is a primary disorder (essential hypertension) in 90-95% of cases or secondary to some identifiable underlying disorder. These diseases are:
· renal parenchymal disease (eg, polycystic kidneys, glomerular or interstitial disease),
· renal vascular disease (eg, renal artery stenosis, fibromuscular dysplasia),
· endocrine disorders (eg, adrenocorticosteroid or mineralocorticoid excess, pheochromocytoma, hyperthyroidism or hypothyroidism, growth hormone excess, hyperparathyroidism),
· coarctation of the aorta,
· oral contraceptive use.
About 20-25% of women with CHP develop preeclampsia –eclampsia syndrome during pregnancy. The condition known as preeclampsia superimposed on pre existing hypertension.
Effect of Chronic Hypertension on Pregnancy
The arterial hypertension primarily affects the condition of fetoplacental complex. Sharp and fast changes of blood pressure have an unfavorable effect not only on mother’s condition, but also on the condition of intrauterine fetus. It is manifested by the increased incidence of premature interruption of pregnancy (early and late spontaneous abortions — in 3 %, premature birth — 12 % of pregnant women). Intrauterine distress and intrauterine growth retardation of the fetus due to chronic insufficiency of blood supply in fetoplacental system develop as a rule. At marked disorders it can result in intrauterine death of the fetus. Disorders of uteroplacental circulation, increased intravascular pressure and increased fragility of vascular wall due to disturbance of its supply at hypertension are the reason of premature separation of normally located placenta, maternal hemorrhages and intrauterine death of the fetus, frequently with development of disseminated intravascular coagulation (DIC) of blood. In 20-36 % of pregnant women with CHP the severe forms of eclampsia develop, hardly yielding to treatment, and also proceeding with phenomena of DIC syndrome.
Typical complications in labor are bleedings connected with placental detachment, abnormalities of labor pains due to failure of blood supply, asphyxia and even death of the fetus, hypertensive crises, and hypotonic bleedings.
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Effect of Pregnancy on Chronic Hypertension
In the 1st trimester of pregnancy a pregnant woman can have a slight decrease of arterial blood pressure, but then a stable increase of blood pressure develops. Exacerbation of the course of idiopathic hypertension is also manifested in acceleration of hypertensive crises. Urinalysis reveals proteinuria, oliguria resulting from stable generalized spasm of microvessels. The excessive physical activity at labor, stressful situation connected with labor on a background of exacerbation of chronic hypertension course are the reason of development of encephalopathy, detachment of retina, failure of cerebral circulation (apoplectic stroke), etc.
Diagnosis of pre existing hypertension
Any hypertension in pregnancy should be evaluated according to diastolic blood pressure (dBP), because it presents peripheral resistance of blood vessels, property of blood supply and it is not as dependent on emotional factors as systolic BP. Hypertension during pregnancy should be recognized in the case of a single measurement of dBP of 110 mm Hg or more; or two consecutive measurements of dBP ≥ 90 mmHg 4 hours or more from each other.
Pre existing hypertension in pregnancy is classified by severity:
· Mild hypertension: dBP 90–99 mmHg, systolic blood pressure 140–149 mmHg.
· Moderate hypertension: dBP 100–109 mmHg, systolic blood pressure 150–159 mmHg.
· Severe hypertension: dBP 110 mmHg or greater, systolic blood pressure 160 mmHg or greater.
Determining whether hypertension, which was detected after the 20th week of pregnancy, is caused by chronic (pre existing) hypertension or preeclampsia, is sometimes a problem, especially if blood pressure was not recorded at the first half of pregnancy. Clinical characteristics obtained through history, physical examination and some laboratory studies can be used to clarify the diagnosis. Laboratory testing to evaluate chronic hypertension (if not done previously or recently) includes testing for target organ damage, potential secondary causes of hypertension, and other risk factors. Thus, diagnosis of CHP is based on:
• Anamnestic data: hypertension before pregnancy
and/or
• Two consecutive measurements of BP of ≥ 140/90mmHg 4 h or more apart if patient is at rest earlier 20th week gestation
or
• ≥ 160/110 mmHg once earlier 20th week gestation.
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